A polyalkylene oxide having an unsaturated end group is useful as a crosslinking agent or a modifier in vinyl polymerization.
The reaction between an unsaturated group-terminated polyalkylene oxide and a hydrosilane having a hydrolyzable group produces a polymer having a crosslinking silicon end group which is useful as a moisture-curing polymer as disclosed in JP-A-52-73998 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
The polyalkylene oxides are, in most cases, required to have a high molecular weight of from about 5,000 to 20,000. However, such a high-molecular weight polyalkylene oxide is not readily available on the market.
JP-A-53-134095 discloses a process for producing an unsaturated group-terminated high-molecular weight polyalkylene oxide, in which a hydroxyl-terminated polyalkylene oxide having a relatively low molecular weight is used as a starting material, which comprises converting the hydroxyl end group to an alkoxide group in the presence of an alkali metal hydroxide (alkoxidation). Thereafter a plurality of the polyalkylene oxide molecules are connected to one another by using a polyhalogen compound to increase the molecular weight of the starting polyalkylene oxide (1st step), and then the hydroxyl end groups are converted to unsaturated groups by using an unsaturated halogen compound. This process is illustrated by the following reaction scheme: ##STR1##
This reference additionally discloses a process in which an alkali metal or an alkali metal compound, capable of producing an alkali metal hydroxide on reaction with water, such as an alkali metal hydride and an alkali metal alkoxide, (hereinafter an alkali metal and an alkali metal compound will be inclusively referred to as an alkoxidizing agent) can be used in place of the alkali metal hydroxide to alkoxidize the hydroxyl end group. Because such alkoxidizing agents have a higher activity than an alkali metal hydroxide, an about equivalent amount of the alkoxidizing agent can be used to conduct the reaction so that purification of the product is easy. However, when the reaction scheme shown above is followed using alkoxidizing agents, the increase in molecular weight and the ability to introduce an unsaturated bond to the product produced in the first step are insufficient, which highligths the fact that the reaction conditions must be strictly controlled before a desired reaction can proceed.